gc: fix func syntax error

Fixes #1685.

R=ken2
CC=golang-dev
https://golang.org/cl/4414042

src/cmd/gc/go.y

@@ -1239,9 +1239,10 @@ fnlitdcl:
 	}
 
 fnliteral:
-	fnlitdcl '{' stmt_list '}'
+	fnlitdcl lbrace stmt_list '}'
 	{
 		$$ = closurebody($3);
+		fixlbrace($2);
 	}
 
 

test/func6.go

+// $G $D/$F.go
+
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	if func() bool { return true }() {}  // 6g used to say this was a syntax error
+	if (func() bool { return true })() {}
+	if (func() bool { return true }()) {}
+}
+